The present invention generally relates to wireless Internet Protocol (IP) networks. More specifically, this invention relates to dynamic allocation of IP addresses for wireless IP network cells.
The advent of wireless IP networks has presented challenging problems in the area of dynamic IP address allocation. Wireless IP networks comprise a plurality of network cells wherein a plurality of handoff and resident hosts communicate with the wireless IP network. Handoff hosts are network hosts whose initial network connection was established in another cell and that subsequently migrate to a new network cell. In contrast, resident hosts are hosts whose initial network connection was established in the present cell and that have not migrated to another network cell. Each network cell further includes a base station that maintains handoff and resident host network connections within the network cell, and facilitates dynamic handoff of handoff hosts within its cell.
The base station within each cell facilitates a network connection with its handoff and resident users through IP addresses assigned to the network hosts within the cell. Thus, an IP address must be allocated to the handoff and resident hosts within a cell to establish and maintain a network connection. The IP addresses dedicated to the handoff and resident hosts can be allocated by methods including an IP address server system(s) that assigns IP addresses for new hosts, and base stations themselves that may determine their own necessary IP address allocation. IP address servers that allocate IP addresses can include servers that are part of a base station itself, or can include IP address servers that are attached to the network and send IP addresses allocations to the base station within a cell. These IP address allocation methods and apparatuses confront a number of problems when allocating IP addresses to handoff and resident hosts within their cells.
First, whenever a host initially establishes a network connection within a cell, the host is considered a resident host, because it establishes its initial network connection within the cell. In order for the resident host to establish its network connection, a base station within the cell must allocate an IP address from the cell""s IP address pool to the resident host. In contrast, whenever a resident host migrates to a new cell after already having its network connection in a prior cell, the host becomes a handoff host, and the new cell must maintain the preexisting network connection of the handoff host. If the new cell has a different IP subnet address relative to the prior cell, the new cell must allocate a new IP address to the handoff host in order to maintain the handoff host""s network connection from the prior cell.
Current dynamic IP address allocation protocols such as Dynamic Host Configuration Protocol (DHCP) treat resident and handoff hosts as equivalent and without preference when allocating IP addresses to these hosts. Thus, a base station may allocate an IP address to a resident host instead of a handoff host, thereby permitting a new resident network connection in place of the prior network connection of a handoff host network, which must be dropped. This equal treatment is obviously undesirable, because denying a resident host an IP address will merely prevent a new network connection, whereas denying a handoff host an IP address causes its preexisting network connection to be terminated. Thus, IP address allocations to handoff hosts should be preferred to IP address allocation of resident hosts in order to facilitate the handoff of preexisting handoff host network connections.
Second, the problem of handoff and resident host network access is further aggravated due to the fact that there is no minimum number of IP addresses that are reserved by individual cells to ensure a certain level of host access. The minimum number of IP addresses available will vary from cell to cell, and thus handoff and resident hosts will have differing degrees of access to the IP network based on the particular cell wherein the host is communicating with the network. As a result, fair access to the wireless IP network for handoff and resident hosts differs from cell to cell, because one cell may have significantly fewer IP addresses to allocate relative to another cell. This is another limitation of present IP address allocation protocols, because it is desirable to ensure fair access of handoff and resident hosts to the network regardless of the particular cell wherein these hosts reside.
In sum, present dynamic IP address allocation protocols for wireless IP network systems suffer from two significant problems. First, these protocols treat resident and handoff hosts equally when allocating IP addresses, thereby causing preexisting handoff host network connections to be dropped in favor of new resident host network connections, when it is preferable to preserve a preexisting handoff host network connection by denying a new resident host network connection. Second, there is no minimum number of IP addresses allocated to individual cells, thereby causing fair access problems when different cells provide different numbers of IP addresses for handoff and resident hosts, thereby making network access arbitrarily dependent on the cell in which the handoff and network host reside.
These and other deficiencies in wireless network dynamic IP address allocation protocols are addressed by the present invention, which is a method and apparatus for dynamic IP address allocation for wireless base stations based on priorities and guard bands.
The method of the system described herein includes several features. First, the total IP address pool of IP addresses for each cell is dynamically determined based on factors including base station demand, thereby ensuring adequate network access from cell to cell. Second, each cell is guaranteed a minimum number of IP addresses for its IP address pool, thereby ensuring a certain level of fair access to the network regardless of the cell wherein a host resides. Third, every cell includes a dynamic guard band of IP addresses reserved exclusively for handoff hosts, thereby mitigating handoff host network connection drops from cell to cell. Fourth, the allocation procedure for IP addresses prioritizes hosts that request IP addresses by favoring handoff hosts over resident hosts when allocating IP addresses, thereby maintaining preexisting network connections of handoff hosts instead of establishing new network connections of resident hosts.
The method herein described is predictive, wherein the size of the IP address pool and guard band for each cell is determined by anticipating handoff and resident host demand on the cell before these hosts actually arrive. Demand predictions for these hosts are based on a number of factors including statistical assessment of IP address demand over time, such as prior days, weeks, and months, as well as real-time factors such as handoff and resident host data traffic levels and demand, and the numbers of handoff and resident hosts.
The prioritization method herein described assigns different priorities to hosts that request an IP address from the present cell and then allocates an IP address to those hosts with a higher priority before those hosts with a lower priority. Thus, in order to prefer handoff hosts over resident hosts, handoff hosts are assigned a higher priority level over resident hosts and are allocated an IP address before resident hosts. In addition, handoff hosts are also inherently preferred over resident hosts due to the fact that a guard band of IP addresses is reserved exclusively for handoff host network connection handoffs within each cell.
The apparatus used to implement this system is an IP address server system that predicts the IP address pool and guard band for each cell base station, establishes an IP address pool based on the anticipated demand, prioritizes host requests for IP addresses, and allocates IP addresses to hosts based on factors including their priority and whether they are a handoff or resident host. Implementation details for the IP address server system vary according to whether the system includes shared and/or dedicated IP address servers. Shared IP address servers predict and allocate IP addresses for multiple base stations within cells, whereas dedicated IP address servers predict and allocate IP addresses for their individual base station.
In a shared IP address server system, a plurality of base stations share a pool of IP addresses with the same subnet address. The shared IP address server predicts the IP address pools and guard bands for each base station, and allocates the IP addresses for each base station accordingly. Thus, the shared IP address server centrally coordinates and allocates IP addresses for the plurality of base stations that it serves.
In the alternative, each base station can perform its own IP address pool and guard band prediction and report the results to the shared IP address server, which makes a final decision on each base station""s IP address pool and guard band size based on the aggregate predictions from the base stations. Thus, some of the processing demands to predict IP address pool and guard band size are offloaded from the shared IP address server to individual base stations, but the shared IP address server still makes the final determination of the IP address pool and guard band size for each base station from an overall system perspective.
In a dedicated IP address server system, each base station includes its own dedicated server that independently predicts and determines its own IP address pool and guard band size subject to the limitations of overall system IP address availability. Such limitations guarantee fairness through mechanisms including a maximum limit on the number of IP addresses each cell can use. In order to dynamically adjust IP address pool and guard band size, each dedicated IP address server/base station can communicate with other dedicated IP address servers and base stations to communicate their IP address needs. Such communications allow individual base stations and dedicated IP address servers to respond to dynamic conditions, such as high IP address demand, by borrowing IP addresses from other dedicated IP address servers and base stations when necessary.
Both shared and dedicated IP address server systems prioritize hosts that request IP addresses from the base station/IP address server, and then serve those hosts with a higher priority first. Thus, by assigning handoff hosts a higher priority relative to resident hosts, the IP address server allocates IP addresses to handoff hosts prior to resident hosts, thereby preventing dropped handoff host network connections at the expense of new resident host network connections.